BTW, IMFdb.org did list Indiana Jones carry revolver as a Webley Army .455 caliber. It's a huge handgun for the era.
If I recall, Jones used a old S&W .45 DA revolver in the other movies & in the "Raiders" bar fight scene, Indy packed a P-35 9x19mm pistol as a BUG-2nd gun.

If you get the new Blu-Ray set, watch the scene in frame by frame.
For years, I thought Jones used a old 1911 .45acp since a early scene with MI/Army Intel officers bring up his military service.